Deashing petroleum residua



March 20, 1951 Glycerine Sulfuric Acid lPreferred= 66 Be'l Filed Feb. 25, 1950 Alkaline Residuum Mixer Mixer Vaporizer Water Vapor Separator Salt Crystals De-ashed Residuum INVENTQR. EVAN E. DAVIS ATTORNEYS.

Patented Mar, 20, 1951 DEASHING PETROLEUM RESIDUA Evan E. Davis, Chester, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Application February 25, 1950, Serial No. 146,222

3 Claims. 1

This invention relates to the treatment of petroleum residual oils for the purpose of removing inorganic matter and reducing the ash content. The invention more specifically relates to a method of treating petroleum residua which contain alkaline naphthenates, whereby the naphthenates are neutralized and the resulting salt is obtained in the form of relatively large crystals which may readily be separated from the treated oil.

In refinery practice it is customary to subject the crude petroleum to a topping operation wherein the lower boiling fractions such as gasoline, kerosene and gas oil are distilled off and then to treat the reduced crude with an alkali, such as caustic soda, preliminary to subjecting it to further distillation under vacuum to remove the lubricating oil fractions. Treatment of the reduced crude with alkali converts any naphthenic acids which are present into alkaline naphthenate soaps. In the subsequent vacuum distillation step the alkaline naphthenates do not distill but rather remainin the bottoms or residuum from the operation in admixture with high boiling hydrocarbons and asphaltic material. Consequently, the residuum product will have a high ash or inorganic content which reduces its value for use as fuel oil. For exam-pie, in the practice of a process of this type such as described in Pew Patent No. 1,761,153, it has been that residual oils have great emulsion-formingtendency, even after neutralization of the naphthenates, probably due to the presence of asphaltic compounds. Consequently, neutralization of the soaps followed by extraction of the salt with water has been found to be more or less unsuccessful.

One effective method of de-ashing residual stocks is disclosed and claimed in Hughes appli 2 cation S. N. 62,371, filed November 27, 1948. According to such method the residual oil is treated at elevated temperature with aqueous sulfuric acid containing 60-67% H280; to substantially neutralize the naphthenates and water is then vaporized fromthe mixture. This procedure causes the inorganic salt resulting from the neutralization to take the form of relatively large size crystals 'which can readily be separated from the oil by settling, filtering or the like. On the other hand, if such procedure is followed by sulfuric acid containing more than about 67% H2804 is utilized, effective de-ashing is not achieved, apparently for the reason that the salt crystals obtained are of extremely small size. In fact, when concentrated acid is used, such as 66 B. sulfuric acid (93% H2804), practically no salt removal is obtained even though the neutralized mixture is allowed to stand at elevated temperature for an exceedingly long time such as several days.

I have now found that petroleum residua can be effectively de-ashed in improved manner by first mixing the oil with a small amount of glycerine such as 0.1-2.0% by volume of the oil, then neutralizing the alkaline naphthenates with sulfuric acid of high concentration, and vaporizing water from the mixture. The presence of glycerine in small amount during the neutralization step causes the inorganic salt, after water has been removed from the mixture, to have relatively large crystal size. This salt can easily be separated from the, oil by settling, filtering or the like.

The use of glycerine in accordance with the present invention thus permits the neutralization to be carried out with strong sulfuric acid. This is much better for plant practice than employing more dilute acid such as 60-67% H2804, as dilute acid gives rise to corrosion problems and generally requires the use of special equipment in handling. By effecting the neutralization with a 4 small amount of glycerine present in the residuum, concentrated sulfuric such as 66 B. acid, which can readily be handled in conventional refinery equipment without corrosion difficulties, may be utilized, and at the same time eflicient removal of the inorganic matter is obtained.

The accompanying drawing schematically illustrates the process according to the present in- 3 vention. The charge material is a residuum stock derived from naphthenic base crude and containing sodium naphthenates. The following are typical properties of this type of material:

S. U. visc. at 210 F.=3000-6000 A.P.I. gravity-=-l1 Ash content=2-3% Referring to the drawing, the first step in the process comprises. mixing the charge with a small amount of glycerine. This step is schematically indicated by mixer [0. The charge should be at a sufficiently elevated temperature to avoid excessive viscosity so that mixing may readily be elfected; for example, temperatures within the range 200-550 F. are suitable. If desired, the charge may be diluted with a lower boiling oil to reduce the viscosity. The amount of glycerine that should be introduced may vary with the particular charge stock being treated and with the degree of de-ashing desired, but in any case the amount should be at least 0.1% by volume of the charge. Larger amounts generally result in improvement in salt removal but usually no advantage is gained by employing more than 2.0% glycerine. Preferred proportions of glycerine are from about 0.2% to about 1.0%.

The mixture of charge and glycerine is then mixed at elevated temperature with sulfuric acid in amount sufficient only to substantially neutralize the residuum, thereby liberating naphthenic acids and forming sodium sulfate. This step is indicated by mixer II. It is preferable that the amount of acid used be at least sufficient to approach complete neutralization without exceeding the amount required for that purpose, but it is of course not necessary that exact neutrality be reached. Any part of the naphthenate soaps which is not neutralized will remain in the residuum during the subsequent steps of the process and will result in a higher ash content of the product.

As previously indicated it is preferred to carry out the neutralization with concentrated sulfuric acid such as 66 B. acid. However, more dilute acid may be used if desired. The presence of glycerine not only will cause efficient removal of the salt when acid of any strength between 67% and 93% is used but also will improve the deashing when acid of strength below 67% is employed. While effective removal of salt in the latter case can be achieved without glycerine, the presence of glycerine permits the use of shorter settling times for separating the salt from the treated residuum.

After neutralization the residuum is subjected to a vaporization step, indicated by vaporizer !2, for the purpose of removingwater. This water derives from the water in the sulfuric acid used and also may be due in part to neutralization of free alkali hydroxide which often is present in the charge material. It is believed that the formation of salt crystals of relatively large size capable of ready separation is obtained during the vaporization step.

Following the vaporization step, the dehydrated mixture is passed into a separator l3 for removal of salt crystals. This may be done in any suitable or conventional manner such as by gravity settling, filtration or centrifuging. The preferred method is merely to pass the mixture into a settling tank, wherein the salt crystals settle to the bottom leaving de-ashed residuum as the upper layer which may be continuously withdrawn.

The following examples illustrate the advantage of using glycerine according to the present process:

Example I Saybolt furol vise. at 210 F.=409 A. P. I. gravity=l0.0 Sulfated ash content=2.95%

It wasfirst mixed with 1.0% glycerine by volume and the mixture was then treated at about 250 F. with sufiicient 66 B. sulfuric acid to approximately neutralize the residuum. Water was permitted to evaporateand the dehydrated mixture was settled for one hour at a temperature of about 250 F. The oil layer was tested and found to have a sulfated ash content of only 0.05%. Thus, about 98% of the ash content was removed with only one hour settling.

Treatment of the charge stock in a similar manner but without the addition of glycerine resulted in no appreciable removal of salt even after permitting the neutralized residuum to stand overnight.

Example If Another batch of the same alkaline residuum as used in the preceding example was mixed with 0.5% glycerine and 0.5% water and the mixture was neutralized at about 300 F. with 66 B. sulfuric acid. Water was permitted to vaporize ofi and the mixture was then settled for hour at about 300 F. The oil layer wasfound to contain 0.12% sulfated ash.

Example III Another batch of the alkaline residuum was mixed with 0.25% glycerine and then treated at 300 F. with sufficient 66 B. sulfuric acid for neutralization. Upon permitting the water to evaporate and settling the-mixture at 300 F., the following results were obtained:

sulfated ash content, per cent by wt. After 1 hr. settling 0.56 After 6 hrs. settling Trace It should benoted that the present invention may not be practiced by first neutralizing the charge with sulfuricacid and then adding the glycerine. When such procedure is followed, the addition of glycerine eifects no improvement in salt removal. It'is essential that the glycerine be present at the time the neutralization is carried out in order for it to exert its beneficial effect.

I claim:

1. Process for treating petroleum residuum containing alkaline naphthenates to remove inorganic matter which comprises mixing the residuum with 01-20% glycerine-by volume, treating the mixture at an elevated temperature with sulfuric acid in amount sumcient only to substantially neutralize the residuum, vaporizing water from the treated residuum, thereby obtaining salt crystals of relativelyv large size, and separating said crystals from thetreated residuum.

2. Process for treating petroleum residuum containing alkaline naphthenates to remove inorganic matter which comprises mixing the residuum with 0.1-2.0% glycerine by volume, treating the mixture at a temperature above200 F. with concentrated sulfuric acid'in amount sufii cient only to substantially neutralize the residuum, vaporizing water from the treated residuum, thereby obtaining salt crystals of relatively large size, and separating said crystals from the treated residuum.

3. Process for treating petroleum residuum containing alkaline naphthenates and having an ash content in excess of 2.0% to remove inorganic matter which comprises mixing the residuum with from about 0.2% to about 1.0% glycerine by volume, treating the mixture at a temperature above 200 F. with concentrated sulfuric acid in amount sufiicient only to substantially neutralize the residuum, vaporizing Water from the mixture, thereby obtaining salt crystals 6 of relatively large size, and permitting the mixture to stand at a temperature above 200 F. for a time sufficient to settle out most of the salt and reduce the ash content to less than 0.3%

EVAN E. DAVIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,950,739 Morrell Mai". 13, 1934 2,009,710 Goodwin July 20, 1935 

1. PROCESS FOR TREATING PETROLEUM RESIDUUM CONTAINING ALKALINE NAPHTHENATES TOREMOVE INORGANIC MATTER WHICH COMPRISES MIXING THE RESIDUUM WITH 0.1-2.0% GLYCERINE BY VOLUME, TREATING THE MIXTURE AT AN ELEVATED TEMPERATURE WITH SULFURIC ACID IN AMOUNT SUFFICIENT ONLY TO SUBSTAN- 